Add CI workflow for lint + typecheck on push/PR

[jeremylongshore]

I noticed that biome check and check-types (tsc) scripts exist at the package level, but release.yml is the only GitHub Actions workflow — there's no quality gate running on push or PR.

A lightweight CI workflow that runs these existing checks would catch type errors and lint issues before they hit main. Something like:

name: CI
on:
  push: { branches: [main] }
  pull_request: { branches: [main] }
jobs:
  quality:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: oven-sh/setup-bun@v2
      - run: bun install --frozen-lockfile
      - run: bun run check
      - run: bun run check-types

No new tools, no new opinions — just automating what already exists.

I'd be happy to submit a PR if this would be useful.